Engine Air Leak from PCV Tube

Some 2019-2020 Silverado 1500 and Sierra 1500 models equipped with the 5.3L V8 engine (RPO L84) may have a rough idle, lean running concern, or an air leak from the Positive Crankcase Ventilation (PCV) system. DTCs P0171 (Fuel Trim System Lean Bank 1) and/or P0174 (Fuel Trim System Lean Bank 2) may be set. These conditions may be caused by an incorrectly installed or damaged foul air PCV tube.

If these conditions are present on a vehicle, check to see if the foul air PCV tube is installed and seated correctly. In the graphic, #1 shows the connector to rocker cover PCV tube location, while #2 shows the connector to intake manifold PCV tube location. (Fig. 14)


Fig. 14


If the tube is installed correct, perform a smoke test using the GE-52250 Variable Pressure Leak Detector (Power Smoke Diagnostic Leak Detector) or equivalent to confirm there are not any leaks.

TIP: The GE-52250 is not currently an essential tool, but it is available through the GM Loan Tool Program. Refer to Bulletin 16-NA-158 for more information about the Loan Tool Program.

If no smoke is detected, pull on the PCV tube ends at the rocker cover or intake manifold to ensure each tube is seated. If a tube is not fully seated, secure the connection by pressing the tube in until it clicks.

If smoke is detected at the rocker cover or intake manifold, remove and reinstall the same PCV tube, ensuring that both latches click to that the tube is fully seated. Repeat the smoke test to verify the condition. If the leak is still present, remove the tube and inspect the O-ring seals. Look for any damage or missing O-ring seals. Replace the tube if any damage is found.

If the tube is cracked, or there is damage at any other location other than at the rocker cover or intake manifold, remove and replace the damaged tube with a new tube.

After completing repairs, clear the DTCs, start the vehicle and idle for five minutes. Turn off the engine and repeat idling the engine for another five minutes.

If the condition is still present or the DTCs return, follow the appropriate Service Information to continue with diagnosis.

If the condition is not present and the DTCs do not return, the PCV tube was not correctly seated during assembly.

For additional information, refer to #PIP5686A.


– Thanks to Raymond Haglund

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